This invention relates to a tubeless pneumatic tire and to a cylindrical noncord nonreinforced carcass subassembly 10A for the pneumatic tire as an intermediate article of manufacture. The subassembly 10A in its unvulcanized state is formed into a cylindrical shape at a tire building station and is a subassembly of a pneumatic tire. The invention is described in relation to a radial ply passenger tire, but it is applicable to light truck, medium truck, agricultural, off-road and other radial or bias ply tire constructions.
Historically, the pneumatic tire has been fabricated as a laminate structure of generally toroidal shape having beads, a tread, belt reinforcement and a carcass. The tire is made of rubber, fabric, and steel. The manufacturing technologies employed for the most part involve assembling the many tire components from flat strips or sheets of material. Each component is placed on a building drum and cut to length such that the ends of a component meet or overlap creating a splice.
In the first stage of assembly the carcass would include one or more plies, and a pair of sidewalls, a pair of apexes, an innerliner (for a tubeless tire), a pair of chafers and perhaps a pair of gum shoulder strips. Annular bead cores can be added during this first stage of tire building, and the ply or plies can be turned around the bead cores to form the xe2x80x9cply turnups.xe2x80x9d
The carcass components (excluding the bead cores) would be either xe2x80x9cbutt splicedxe2x80x9d or xe2x80x9clap spliced.xe2x80x9d A butt splice has the component ends joined but not overlapped, a lap splice has overlapping ends.
This intermediate article of manufacture would be cylindrically formed at this point in the first stage of assembly. The cylindrical carcass is expanded into a toroidal shape after completion of the first-stage of tire building that results in such cylindrical intermediate article of manufacture. Reinforcing belts and the tread are added to the intermediate article during a second stage of tire manufacture, which can occur using the same building drum or work station or at a separate shaping station.
During the expansion of the carcass, tensile stresses are imposed on the spliced and uncured components of the tire carcass.
In the case of passenger tires, lap splices of the plies were preferred because the splice remained intact whereas butt splices would tend to open or fail. Butt splices were preferred for the commercial or medium truck tires. Even with the good adhesion of the lap splice the cords adjacent the splice tended to be stretched compensating for the overlapped two layers of cords at the splice. This localized stretching creates a nonuniformity that is readily visible under x-ray, ultrasonic display, or by physically cutting the tire and visually inspecting it.
The tire designer, in order to prevent the creation of tire uniformity problems, has historically insured that the splices of the various layers of components were not circumferentially aligned. This nonalignment of splice joints was believed to improve the carcass overall durability and uniformity, as measured by the amount of force variation and the balance of the tire. Tire engineers also have believed that tire uniformity could be improved if these discontinuities were deliberately circumferentially spaced around the carcass.
The subject matter of this patent application completely reverses this conventional wisdom as it relates to unreinforced subassembly construction. The unreinforced subassembly is manufactured with numerous components having a common splice line. The tire casing built with the subassembly according to the present invention can be built more efficiently while reducing splice-related nonuniformities.
An unvulcanized noncord reinforced subassembly 10 for incorporation in a tire casing as an intermediate article of manufacture, is disclosed. The subassembly has a liner having a pair of lateral ends defining the axial width (WL) of the liner and a plurality of elastomeric components attached to the liner or another of the elastomeric components. The plurality of elastomeric components includes a pair of chafers, one chafer being attached to and overlapping each of the lateral ends of the liner, a pair of sidewalls, each sidewall having a non-linear contoured profile on one surface, each sidewall being axially spaced from the liner and attached to and overlapping the chafer.
The liner and the elastomeric components have a pair of lateral ends defining the axial width (W) of the casing subassembly. The liner and the elastomeric components each have a predetermined cross-sectional profile having lateral edges at predetermined locations along the length of the casing subassembly. Each component is formed and attached while hot at the location where formed, thereby fixing the location of the lateral edges of each component to form a casing subassembly. The casing subassembly is adapted to be cut to length with common ends being spliced along a substantially flat plane, extending thus through the article across the axial width (W). The formed casing subassembly is adapted to accept a ply and a pair of annular bead cores positioned onto the casing subassembly at a latter stage of building the tire.
The above-described subassembly 10 is cut from a laminate 10A. The laminate 10A has at least two components laminated together, the components being selected from one or more of the component types consisting of a liner 50, a chafer 60, a sidewall 70, a whitewall strip 80, a cover strip 90 and a gum shoulder strip 40. The laminate 10A has a width (W), a pair of ends 12,14, the distance between the ends defining the subassembly length (L). The components have common ends 12,14 spliced along a substantially flat plane (P), the plane (P) extending through the article across its axial width (W). The splice or flat plane (P) is inclined at an angle xcex8, xcex8 being less than 90xc2x0 and greater than 60xc2x0 relative to a normal plane (NP) passing through the laminate and extending. In a preferred embodiment of the invention the splice or flat plane (P) is inclined at an angle xcex8 of about 80xc2x0. This orientation of the splice permits the ends 12,14 to have large uncured surface areas which upon assembly greatly increases adhesion of the joint. Ideally for manufacturing efficiency and improved product quality it is preferable that each of the components listed above in the quantities required to assemble the subassembly be spliced along a straight linear surface as described above.